It is known that, in modern processes for the preparation of rubber compounds, a system is employed consisting of a closed mixer, commonly called “Banbury mixer”, paired with a twin-screw extruder called “Dump Extruder” (FIG. 5). The system provides that the raw material, typically rubber, or a silicone-based polymer, is mixed with fillers and various additives in a closed Banbury-type (from the name of its inventor) mixer, from which, at regular intervals, an evenly-mixed compound comes out, called “batch”, which falls into the feedbox of the dump extruder lying below.
In other words, during operation, the closed mixer delivers at regular intervals batches of compounded material to the dump extruder, which has instead the function of transforming the compound batch so prepared—typically coming out in the shape of a continuous strip or leaf; this is subsequently cooled and sent to the following processing steps.
Alternatively to this system, the step of the preparation of the compound to be extruded can be carried out in an open cylinder mixer: however, in order to obtain a good batch, this type of mixer requires an operator to be present at all times handling the material to be compounded by cutting and reintroducing the compound into the mixer where necessary.
The cylinder mixer is a bulky, expensive and non-automatic machine, and exposes the operator to a high level of injury hazard.
The object of the present invention is to overcome these disadvantages by supplying a machine that does not need an open cylinder mixer for the preparation of the rubber compound or silicone-based material.
Such object is achieved by means of a machine as described in its essential features in the attached main claim.
Other inventive aspects of the machine and method thereof are described in the dependent claims.